Easy-open tear strip reinforcing means

ABSTRACT

D R A W I N G A COINED INDENTATION AT THE BENDING LINE OF AN EASYOPEN CAN END TEAR STRIP. THE INDENTATION HAS NEARLY VERTICAL SIDE WALLS OF INCREASED THICKNESS AND THE METAL BETWEEN THE COINED AREA AND THE TEAR-STRIP SEVERING SCORE IS IN COMPRESSION. THIS PREVENTS THE FORMATION OF CRACKS IN THE SCORE AND INCREASES THE STRENGTH OF THE STRIP TO PREVENT ITS BREAKING WHEN A CREASE IS FORMED WHEN THE CAN IS OPENED IMPROPERLY.

May 23, 1972 BROWN ET AL 3,664,543

EASY-OPEN TEAR STRIP REINFORCING MEANS Filed Oct. 8, 1970 mlVf/Vfd'Q 0010/ 1. 8/040? frmd/ C. fra ze United States Patent 3,664,543 EASY-OPEN TEAR STRIP REINFORCING MEANS Omar L. Brown, Kettering, Ohio, and Ermal C. Fraze, 355 W. Stroop Road, Dayton, Ohio 45429; said Brown assignor to said Fraze Filed Oct. 8, 1970, Ser. No. 79,218 Int. Cl. BZld 51/38 US. Cl. 220-54 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The present invention relates to a means for increasing the ability of an easy-open can end tear strip to withstand bending without fracturing. More specifically, the invention relates to a method of increasing the strength of a tear strip in an area therein within which sharp creases tend to form in such can ends when the cans are improperly opened by a user.

Cans having easy-open can ends have become very common in the recent past for packaging beverages, etc. Basically, these cans comprise an end wall which is suitably attached to the upper periphery of a can body so as to enclose the volume contained within the can. A removable portion or tear strip is formed in the can end by means of a weakening score which may be ruptured when the can is to be opened. A tab is attached to the tear strip, by any suitable means such as an integral rivet, at a position which is rather close to the weakening score so that when the tab is lifted, initial rupturing of the score occurs.

The person opening the can pulls the tab upwardly so as to continue the severing of the tear strip from the can end until either a pour spout is formed or a full panel pull-out comprising a major portion of the can end is removed.

Tabs in common use today generally comprise a Washerlike member forming a rigid lever which acts against the can end in the area closely adjacent the rivet when a person opening the can lifts the tab. Normally, the rupture begins to occur before the tab is raised through a very large angle and the person opening the can then puts his finger into the central opening of the tab: and, by exerting an upward force relative to the can, completes the severance of the score for removal of the tear strip.

Unfortunately, some users have a tendency to lift and also rotate the tab through a relatively large anglesometimes as great as 1180--in order to rupture as much of the score as they can during the initial opening action. They then must rotate the tab back toward its initial position so that they can insert their finger into the tab opening to commence the pulling action.

3,664,543 Patented May 23, I972 Under the normal pressures of competition, it has become necessary to reduce the cost of such can ends and one of the more popular courses of action in accomplishing this result has been to provide them with greater tensile strength so that the thickness of the end wall can be reduced accordingly. In other words, the can ends are thinner but are proportionately stronger than those originally used. However, this combination of properties also causes them tobe more brittle.

Since the end wall, and consequently the tear strip, are relatively thin, the rotation of the tab through a large angle causes a relatively sharp crease to be formed in the tear strip metal along a bending line which is closely adjacent the attachment rivet and directly below the tab leverage point. This line is usually rather short'in length since the opposite portions of the rupturing score are very closely spaced in that area. Since the tear strip metal is very brittle due to the reasons described above, the stresses created along the bending line when the tab is rotated through a large angle are often great enough to cause the tear strip to break along that line when the tab is rotated back toward its initial position.

As a result, the person opening the can in this manner is unable to remove a major portion of the tear strip since the crease which breaks is very close to the position in which the score is initially ruptured. When this occurs, a pliers or other tool must be used to remove the remaining portion of the tear strip or the product must be dispensed through the small opening resulting between the initial score-rupturing position and the crease, if possible.

Additionally, if the grain structure of the tear strip extends in the general direction of the length of the strip, pulling on the tab to remove the strip can cause it to be torn along a diagonal parallel to the grain. In other words, the tear strip can itself be torn into two parts one of which is removed from the can end with the tab and one of which remains in position obstructing content removal and presenting a dangerously sharp edge.

In the past, attempts have been made to increase the width of the bending line, so as to prevent the formation of the sharp crease, by installing a reinforcing bead in the area in which the crease is normally formed and which extends in the general direction of rotation of the tab. These beads have been formed, simultaneously with the formation of the score, by a punching-type operation which deforms and stretches metal in the tear strip to form an oifset bead or panel across the crease area.

This stretching of the tear strip metal causes its thickness to be reduced still further and the metal remaining between the bead and the score is thereby placed in tension. The reduction of the thickness of the tear strip reduces its ability to withstand bending and a sharp, easily broken crease may still be formed therein. Even more importantly, however, since the metal between the bead and the score is in tension, it has been found that the bead formation results in microscopic cracks being formed in the score so that air-contamination of the contents of the can can occur, or, for example, a beverage in the can can go flat.

SUMMARY OF THE INVENTION According to the concepts of the present invention, a portion of the tear strip in the area in which the crease is normally formed, and about which the tab-lever pivots,

is provided with a bead by means of a forming or coining operation which commences just prior to the time that the tearing score is formed in the end panel as the tools move toward and can end.

The coining operation begins to take place and causes metal to flow from the bottom of the coined area into the nearly vertical walls thereof and also into the portion of the tear strip between the coining and the score, even before the scoring begins. As a result, to a large extent, rather than thinning the tear strip between the bead and the score, the displacement metal is arranged so as to produce greater strength therein. The area between the coined bead and the score is placed in compression by this operation, thus obviating the possibility of the formation of microscopic cracks in the score, thereby preventing contamination of the can contents, while allowing even improper opening action to be sustained by the tear strip without a break being formed in the strip before it is fully removed from the end panel.

Further, the coined bead strengthens the tear strip and, apparently, realigns enough of the grain thereof near the integral rivet to prevent diagonal tearing of the strip as it is pulled away from the can end.

Other advantages, objects, and embodiments of the present invention will become obvious to those skilled in the art by perusal of the detailed description and accompanying drawing which illustrate what is presently considered to be a preferred embodiment of the best mode contemplated for utilizing the novel principles of the invention as set forth in detail in the claims.

BRIEF DESCRIPTION OF THE INVENTION FIG. 1 is a top plan view of an easy-open can end incorporating the present invention;

FIG. 2 is an enlarged cross sectional illustration of a can end, such as that shown in FIG. 1, illustrating the manner in which the can end is coined and scored during formation thereof; and

FIG. 3 is a sectional view of the tear strip of the can end shown in FIG. 1, taken along the line III-III thereof.

DETAILED DESCRIPTION A can end 11, shown in FIG. 1, is provided with an attachment portion 13 by which the end is attached to a can body (not shown). Within the periphery of the attachment portion 13, a center panel 15 is provided with a score 17 which outlines or defines a removable tear strip 19.

A tab 21 of any suitable type is fastened adjacent one end of the tear strip 19 by an integral rivet 2.3 in the now well-known manner.

As shown in FIG. 1, a line III-III generally defines a primary bending line about which the tear strip 19 will bend when the tab 21 is lifted during opening of the can. In prior art cans, movement of the tear strip from the position shown to a second position in which it overlies the tear strip causes a sharp crease to form along the line along which the strip bends. When the tab is rotated back toward the illustrated position, the strip tends to break along the crease and the rivet and tab become completely separated from the major portion of the tab. When this occurs, it is exeremely difficult to remove the tear strip without employing a pliers or other similar tool.

According to the present invention, however, a coin segment 25 may be formed in the area of the bend line and is so constructed that it will increase the width of the bend line sufiiciently to tend to prohibit the formation of the sharp crease by movement of the tab in the manner described. Although the segment 25 is indicated as being circular, it should be realized that it may be of any desired or suitable configuration so long as it seems to increase the width of the bend line in the manner described here.

As shown in FIG. 2, a scoring die 41 having a scoring tool 43 thereon corresponding to the outline of the score 17 in FIG. 1 may be positioned above the central panel 15 of a can end to be formed. A coining tool 45 is positioned within the tool 43; the working structure is cooperatively positioned over a die 47 having a coining indentation 49 therein.

As shown, the coining tool 45 extends beyond the face of the die 41 a slightly greater distance than does the leading edge of scoring tool 43. Therefore, when the coining tool enters into contact with the panel, the can end begins to deform by forcing metal in the area of the coining tool radially outwardly therefrom and downwardly into the indentation 49. This flow of metal will continue as the die 41 is lowered until the panel contacts or approaches contact with the bottom of the indentation.

The coining tool will cause the metal to flow outwardly so that the bottom 51 of the coined area 25 will be substantially reduced in thickness while the nearly vertical side wall 53 thereof is increased in thickness. Further, the coined metal also flows into a portion of the tear strip between the coining and the score so as to increase the cross section thereof. The amount of increase diminishes as the radius from the coining increases; this is clearly illustrated in FIG. 3.

On the other hand, when the scoring tool 43 contacts the panel 15, metal will be forced away from the score line 17 and inwardly toward the coined area 25.

In this way, the portion of the panel between the coined area and the score will be placed in compression so that the stresses remaining in the metal tend to force it toward both the coined area and the score, obviating the possibility of formation of microscopic cracks in the score which may allow contamination of the can contents.

Further, the increased thickness of the wall 53 causes an increased tube-like rigidity within the coining 25 so that the bend line is increased in its width and the tear strip becomes much stronger and less susceptible to the formation of a rupturable sharp crease.

In this manner, the applicants have provided an embodiment of a new and improved concept in the can art which yields a true advancement in that art. Many other embodiments, modifications, and alterations within the scope of the present invention will be obvious to those skilled in the art, wherefore what is claimed as the invention is:

1. In a container end wall comprising a central panel having a first cross section dimension, a score line therein defining a removable tear strip, and a tab fixed to said ltear strip for rupturing said score by lifting said tab to cause bending of said tear strip along a bend line, the improvement comprising:

a coined area within said tear strip, interesting said bend line, and including a bottom portion having a second cross section dimension which is less than said first cross section dimension and a side wall portion having a third cross section dimension which is greater than said first cross section dimension.

2. The container end wall of claim 1 wherein the portion of said tear strip intermediate said coined area and said score line is in compression.

3. The container end wall of claim 1 wherein the portion of said tear strip intermediate said coined area and said score line has a mean cross section dimension which is greater than said first cross section dimension.

4. The container end wall of claim 1 wherein the portion of said tear strip intermediate said coined area and said score line has an area of variable cross section which is larger in thickness at any portion thereof than said first cross section dimension.

5. The container end wall of claim 1 wherein the portion of said tear strip intermediate said coined area and said score line has a variable cross section, the average thickness of which is greater than said first cross section dimension.

6. The container end wall of claim 5 wherein said variable cross section decreases in cross section as the distance from said coined area increases.

6 References Cited UNITED STATES PATENTS 3,478,917 11/ 1969 Rouse et a1 220-54 3,563,199 2/1971 Wolfe 220-54 3,416,698 12/1968 Arfert 22054 GEORGE T. HALL, Primary Examiner 

